This invention relates to a method of and to a device for identifying the angular position of the rotor of a stepping motor, when the rotor is at rest.
The method is applicable to motors comprising a magnetic stator having at least two diametrically opposed poles which can lie in two stable rest positions, a stator making up a magnetic circuit having saturable narrow portions and a coil coupled magnetically to the stator for creating therein a magnetic field interacting with the rotor. Such motors are well-known and are widely used, e.g. in watch-making, to drive the hands via a gear-train. Depending on the shape of the control signals applied to the terminals of the coil, they can also be made to rotate in one direction or in an opposite direction.
Correctly identifying the position of the rotor of a motor can be an essential factor for the proper operation of for example a watch if the motor is of the two directions of rotation type when the polarity of the next drive pulse needs to be ascertained to cause the motor to rotate in the required direction or, if the watch is provided with means for taking-up non-effected steps, to check whether the motor has performed the previous step or not.